STP733: Fourier Transform Techniques—Fracture and Fatigue

    Passoja, DE
    Senior research scientist and project scientist, Union Carbide Corp., Central Scientific Laboratory, Tarrytown Technical Center, Tarrytown, N.Y.

    Psioda, JA
    Senior research scientist and project scientist, Union Carbide Corp., Central Scientific Laboratory, Tarrytown Technical Center, Tarrytown, N.Y.

    Pages: 32    Published: Jan 1981


    Abstract

    Real-time analysis of the fatigue crack growth process has been achieved by means of phase-sensitive signal detection methods used in conjunction with spectrum analysis. During crack growth, modulations of the displacement signal occur as a result of the crack's interaction with the microstructure. It was found that the character of the modulation signals was not random but periodic. Utilization of quantitative fractographic and Fourier transform techniques facilitated the formulation of the relationships existing between the microstructure and the signals measured during fatigue crack growth testing. There is a direct correspondence between the Fourier spectrum of the crack profile and the Fourier spectrum of the displacement modulations; the space-time correspondence between the test and the fracture surface was established by the determination of the microscopic fatigue crack velocity. The spectra of the fracture surface and the displacement modulations arise from secondary cracking along second-phase particles in the Type 7075-T6 alloy that was studied.

    Keywords:

    fatigue, fractography, spectrum analysis, signal processing, Fourier transform methods, aluminum alloys, microconstituents, materials, materials science


    Paper ID: STP33440S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP33440S


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